It is known to use active technologies to perform 3D reconstruction, such as using laser radar. However, since the sensor is not passive, it can be detected and is not covert. Other techniques exist for reconstructing a 3D model of an object from multiple camera views. However, most of these techniques rely on image feature detection and matching, which is a very hard problem.
Furthermore, very few of the existing 3D reconstruction techniques using cameras have addressed the issue of reconstructing objects which are occluded in the input images. Those techniques that have addressed this issue have focused mainly on visualizing an object behind an occlusion, but not obtaining a detailed 3D model of it.